Atomic-force　microscopy　(AFM)　is　a　type　of　scanning　probe　microscopy.　It　possesses　nano-scale　resolution　which　is　＞　1000　times　better　than　the　optical　diffraction　limit.　An　image　of　AFM　is　the　result　of　interaction　between　the　tip　and　the　sample.　The　AFM　image　is　not　accurate　and　distorted　due　to　the　finite　size　of　the　probe　tip.　To　correct　the　AFM　image　and　acquire　accurate　sample　morphology　information,　it　needs　to　evaluate　the　tip　shape　and　status.　The　shape　of　the　probe　tip　is　calculated　to　determine　the　quality　of　the　probe.　The　optical　glass　surface　fabricated　by　free　abrasive　polishing　(traditional　mechanical　polishing)　technique　is　used　as　a　new　tip　characteriser　to　calibrate　the　AFM　probe　tip.　Meanwhile,　an　improved　blind　reconstruction　algorithm　is　adopted　to　calculate　the　AFM　tip　shape　and　size.　In　the　help　of　matrices,　the　blind　reconstruction　algorithm　is　elaborated　clearly.　The　optical　glass　surface　with　irregular　nanostructures　ensures　that　the　morphology　of　probe　tip　can　be　determined　accurately.　Without　independent　knowledge　of　the　sample　morphology,　the　three-dimensional　morphology　of　the　AFM　tip　can　be　obtained.